In an effort to develop a monkey model of rotavirus (RV) infection we have initially characterized natural RV infection in colony reared rhesus monkeys. Feces and serum were collected from 37 diarrheic monkeys of ages ranging from 8 to 61 months. Feces were screened by a PCR assay for group anti-RV and a commercial enzyme immunozassay (EIA). Virus isolation (VI) was performed on feces that were positive by either assay. Anti-RV IGG was quantitated in serum and fecal washes by elisa. RV antigen recognition by serum IGG was determined by immunoblot. Suitable reagents were not available for detection of anti-RV IGA. PCR was more sensitive in detecting fecal RV shedding than EIA. A RV was isolated from one PCR and EIA positive fecal sample. The majority of animals with sera available for testing had IGG titers to RV. The fecal RV positive animals were either serum antibody negative or sera was not available. Generally sera with higher elisa titers recognized more RV viral proteins (VP) by immunoblot. Anti-RV copro-IGG is present in the majority of animals assayed to date. Two animals with anti-RV copro-IGG were fecal RV positive. Natural RV infection in colony reared rhesus monkeys appears similar to natural RV infection in humans.